@HappyHelen ,
They are not that easy to track down. We finally found a source a couple of years ago that had food grade sheets. They have to be extruded
for some reason. We even had them hinge 3 sides for us. The hinges and glue are also food safe. Not sure, they might apply the hing with heat.
We used the tri fold with a piece on the bottom and one on the top. I think is was Professional Plastics thought not sure. I replace everything. We can
turn the tri folds into sugar boxes with ease. We had an X cut into a few tops so we can maneuver the heat lamps around. the even put channels on the top and
bottom. They're easy to carry somewhere and you can set up a sugar box in 2 minutes.
I think the extrusion process makes it plexi through and through. No air. They don't seem to scratch.
We used to have wooden ones covered with SS. Took 3 guys to carry it.